Irrespective whether industrial trucks have a three wheel chassis, four wheel chassis or five wheel chassis, only one single driving wheel is provided at most, which is also a steered wheel at the same time in most cases. For this purpose, the driving wheel is rotatably mounted around a horizontal shaft in a so-called fifth wheel, which is rotatably mounted around a vertical shaft in a second bearing member. With the aid of a steering drive, the fifth wheel is pivoted in relation to the frame-fixed or not turnable bearing member. On the fifth wheel sits a drive motor, which is pivoted together with it and which drives the driving wheel, via a conical wheel- or spur wheel gearbox, for instance.
The driving wheel is often not cushioned, a certain cushioning effect taking place via the tires. It is also known to suspend the driving wheel in a spring-cushioned way and optionally to load or relieve it depending on the load.
In industrial trucks with driver seat, the spring-cushioned suspension of the driving wheel is desired, so that the driver is not subjected to strong shocks. From U.S. Pat. No. 6,488,297 B2, the entire contents of which is incorporated herein by reference, a suspension for an industrial truck has become known, in which that bearing member, in which the bearing member for the driving wheel is rotatably mounted around a vertical axis, is suspended vertically movable by means of a parallel rod assembly. A spring acts on the first bearing member and thus it counter-acts the upward movement of the first bearing member.
The present invention is based on the objective to provide a preassembly unit for the drive of an industrial truck which permits a selectionable connection with the frame of an industrial truck, irrespective of its actual construction. The construction is to be compact, at spring-cushioned suspension of the driving wheel in particular.